Bill Fitzmaurice

Dispersion, dispersion, dispersion. It's inversely proportional to the size of the source. The main reason for larger drivers is they can move more air than smaller drivers. If you use multiple smaller drivers you can move just as much air with higher efficiency and wider dispersion so long as they're vertically aligned. Fifteens work best where dispersion isn't a concern, which means either in sub or in 2 way or 3 way cabs where the fifteen is only run to 800Hz or so.

Do a search. This topic has been thoroughly discussed in multiple threads. It's unfortunate that your guitarist didn't do his homework before buying the DXR15s. You'd get a much better result with a pair of DXR10 and an 18 inch sub.

Playing arenas with no PA? 😄

Avoid that. It makes it harder to hear them, for you and the audience. Vertical sources always work better.

Feet don't affect the sound but they do make the cab more durable. I can't fathom any reason to not have them. However, the Markbass cab corners do extend past the panel, so they do act as feet of a sort. They also interlock when cabs are stacked, so that's the reasoning behind them. For added protection I'd add feet to the cab that's going to be on the bottom of the stack.

No. That's the myth of underpowering, which like Nessie and Robin Hood just won't go away.

It is if you do it right. Our hearing is logarithmic. It takes ten times the power/a 10dB increase in level to sound twice as loud. To account for that volume controls are also logarithmic, commonly referred to as audio taper pots, as opposed to tone controls, which are usually linear taper pots. I've seen amps that used linear taper volume controls, and the result was not linear. But it has nothing to do with the amp class.

That was covered in the thread, starting with the first reply.

Yes, it is, which is why that load must be within the secondary specs. If you want to get really picky about it you match the reflected load current to the primary current, but when you try to do that via the speaker impedance and/or the number of output valves you run into the issue that speaker impedances aren't a fixed value, they vary with frequency and the enclosure design, so you can't really get it perfect. For the most part close enough is good enough so long as you don't have a gross mismatch, like using a 4 ohm tap with a 16 ohm speaker.

The load impedance seen by the power valves is the output transformer primary. All that you accomplish by removing two valves is to reduce the current that the amp can deliver, and while that does reduce the power it's not a good idea. Guitar players who came up with that notion were only fooling themselves as to its effect, which at best might result in a measly 3dB reduction in maximum output.

A compressor that tames the initial transient peaks but doesn't have any other effect should fix the problem. I'd say whatever limiter you're using either can't do that or it's not set up correctly to do that. I used to be able to get my Hartke 3500 to go into protect mode. It certainly wasn't caused by a lack of power or headroom. But I didn't have a compressor, and it only happened when I slammed a chord at the end of a song. It didn't bother things all that much, as my feed to the PA was unaffected.

I hope it works out, but...subs have to be considerably larger than mains, which means heavier, for the same reason that basses have longer necks and larger strings than guitars. Otherwise we'd use guitars tuned an octave lower.

I paid $350 for my '65 Bassman. That was the average monthly wage at that time in the US. I paid the same for my '65 Jazz Bass.

Practical but not inexpensive. Old school drivers have xmax values averaging 4mm. A driver with 8mm xmax is the equivalent of two drivers with 4mm xmax, but they can cost twice as much as well.

But you're the bass player. You're the smart one in the band. At least it's always been that way for me. 😄

The contents of this thread thoroughly explain why tubes and SS are different, and why watts don't define loudness or tone. Folks like agedhorse, Phil Starr and myself have been posting this information for as long as there have been forums to post it on. Can't say we haven't tried.

+1. Whatever you have for tops requires a sub, or subs, with no less than twice the air moving capacity. The average moderately priced twelve top, for instance, has some 250cc cone displacement. That puts a pair of them at 500cc. A reasonable subwoofer match would require 1000cc displacement. That means a moderately priced 18 or a pair of 15s.

Valve amps are the opposite of SS. They have a maximum load impedance, not a minimum. They can even withstand a dead short, while an open circuit can damage them. For this reason one of the output jacks on Fenders was a closed circuit switching jack that shorted the output when there was nothing plugged into the main speaker jack. It also meant no signal passed if you plugged into the extension jack instead of the main jack, which pretty much every Fender owner discovered at some point, to their great consternation.

Watts and loudness are only indirectly related. There are a half dozen factors that have far more effect on loudness than watts, a fact that neither amp nor speaker manufacturers mention in their advertising, because watts drive sales.

Vintage Fenders aren't fussy. We used to run them with anywhere from 8 to 1 ohm loads with never a complaint.

I'd be surprised to see Mesa saying that. Subjectively sounding louder yes, but not more powerful. A watt is still a watt.

With a valve power stage the compression takes place within it, which gives a different result than when it takes before it. There's also a contribution made by the output section power supply, which doesn't happen with SS. For that matter the most sought after valve amps have valve rectification in the power supply, which gives a softer transition into clipping than SS rectification. The addition of SS diodes in place of a 5Y3 or 5U4 valve in Fender amps was one of the reasons why it was said that CBS ruined them, although in truth Fender started using them in some models before the CBS takeover.

The reason is compression. The natural compression of valves reduces the level of transient peaks that cause high level distortion when the amp is at or near full power. It can be approximated with SS using a compressor. It can be very closely approximated with SS using a compressor plus DSP emulation.

Not really. 58Hz f3 is nothing special, nor is 100dB/1w when you have eight of them.

Ampeg is one of the more honest companies, and the 58Hz f3 is accurate, as is the 40Hz f10. They're playing a bit fast and loose when they say 'The Infinite Baffle design of these sealed enclosures produces vast amounts of tightly focused bass.', but nobody's perfect. 😒